Daniel J. McGarvey

A Simple Method to Predict Regional Fish Abundance: An Example in the McKenzie River Basin, Oregon

Abstract Regional assessments of fisheries resources are increasingly called for, but tools with which to perform them are limited. We present a simple method that can be used to estimate regional carrying capacity and apply it to the McKenzie River Basin, Oregon. First, we use a macroecological model to predict trout densities within small, medium, and large streams in the McKenzie Basin. Next, we evaluate the reliability of the predicted trout densities by comparing them with field-measured densities. We then calculate the total surface areas of small, medium, and large streams within the basin and multiply these surface areas by the predicted trout densities to estimate regional carrying capacity. Predicted carrying capacity within the basin is approximately 2.1 million trout (median predicted abundance). Our method requires minimal input data, and much of this data can be compiled from literature sources. The method may therefore have broad utility. This article not subject to U.S. Copyright Law.

Assessing the relative influences of abiotic and biotic factors on American eel Anguilla rostrata distribution using hydrologic, physical habitat, and functional trait data

Species’ distributions are influenced by abiotic and biotic factors but direct comparison of their relative importance is difficult, particularly when working with complex, multi‐species datasets. Here, we compare the relative effects of hydrology, physical habitat, and co‐occurring fish functional traits on the contemporary (1950–1990) distribution of the American eel Anguilla rostrata in six Mid‐Atlantic (USA) rivers. To do so, we implement a null model approach that compares conditions at sites of known American eel presence to a random sample of sites throughout a broader landscape, allowing us to identify variables that may have the strongest influences on American eel distribution. Results suggest that, within this subset of the American eels geographic range, the functional characteristics of locally co‐occurring fishes and habitat fragmentation by dams may have the strongest influences on American eel distribution, compared to other predictor variables included in the analysis. Given the widespread distribution and complex biology of this species, we caution that our results may not apply to all American eel subpopulations or life stages. Nonetheless, the observed importance of co‐occurring fish functional traits may inform American eel conservation and, more generally, provide a means to incorporate biotic influences in research on species’ distributions.

Chapter 16 – Fish Assemblages

Methods to sample fishes in stream ecosystems and to analyze the raw data, focusing primarily on assemblage-level (all fish species combined) analyses, are presented in this chapter. We begin with guidance on sample site selection, permitting for fish collection, and information-gathering steps to be completed prior to conducting fieldwork. Basic sampling methods (visual surveying, electrofishing, and seining) are presented with specific instructions for estimating population sizes via visual, capture-recapture, and depletion surveys, in addition to new guidance on environmental DNA (eDNA) methods. Steps to process fish specimens in the field including the use of anesthesia and preservation of whole specimens or tissue samples (for genetic or stable isotope analysis) are also presented. Data analysis methods include characterization of size-structure within populations, estimation of species richness and diversity, and application of fish functional traits. We conclude with three advanced topics in assemblage-level analysis: multidimensional scaling (MDS), ecological networks, and loop analysis.

U.S. Fish and Wildlife Service is Expecting Multiples

The Endangered Species Program at the U.S. Fish and Wildlife Service (USFWS) recently received some big news. The list of threatened and endangered species is poised to grow. On September 9, 2011, a joint settlement between the USFWS, Wild Earth Guardians, and the Center for Biological Diversity was approved in the District of Columbia U.S. District Court. Under this settlement, the USFWS agreed to process a backlog of more than 700 listing petitions by 2018 (USFWS 2012). Sixty-six of these are for fishes.